The goal of this research is to make a chemical-measurement system for real-time detection of volatile organic compounds (VOCs) using silicon- micromachined components. This microinstrument will be designed for use in personal chemical exposure monitors. It will be small, robust, battery- operated, sensitive enough to detect VOCs at a fraction of the OSHA permissible exposure level and selective enough to identify toxic chemicals in a realistic environment. In Phase I we designed and built a simplified prototype microinstrument. We used this system to measure benzene and toluene concentrations at a fraction of their permissible exposure levels. The system demonstrated selectivity between the organic vapors, and no response to saturated water vapor. In this phase we shall add functionality to the microinstrument to improve chemical selectivity. The microinstrument will be micromachined to reduce size, power and manufacturing cost. A portable measurement system incorporating the microinstrument will be field tested in workplace settings. Our goal is to identify and measure all the VOCs present at each site. PROPOSED COMMERCIAL APPLICATION: This sensor system may be broadly applicable to : personal chemical-exposure monitoring; warfare-agent detection; anesthetic-gas measurement; monitoring and controlling toxic waste remediation; pollutant monitoring to ensure compliance with the Clean Air Act; indoor-air quality monitoring to address "sick-building syndrome" and VOC-caused equipment damage.